Coating composition having a high scratch resistance and weathering stability

ABSTRACT

The present invention relates to a coating composition comprising
         (a) at least one hydroxyl-containing compound (A),   (b) at least one compound (B) having free and/or blocked isocyanate groups, and   (c) at least one phosphate-containing catalyst (C) for the crosslinking of silane groups,   (d) at least one further catalyst (D),
 
one or more constituents of the coating composition containing hydrolyzable silane groups, wherein the catalyst (D) is a bicyclic amine.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Phase Application of Patent ApplicationPCT/EP2008/010810 filed on 18 Dec. 2008, which claims priority toDE102007061855.9, filed 19 Dec. 2007, both of which are herebyincorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to coating compositions comprising

-   -   (a) at least one hydroxyl-containing compound (A),    -   (b) at least one compound (B) having free and/or blocked        isocyanate groups, and    -   (c) at least one phosphorus catalyst (C) for the crosslinking of        silane groups,    -   (d) at least one further catalyst (D),        wherein one or more constituents of the coating composition        contain hydrolyzable silane groups.

BACKGROUND OF THE INVENTION

WO-A-01/98393 describes 2K (2-component) coating compositions comprisinga polyol binder component and a polyisocyanate crosslinker componentpartly functionalized with alkoxysilyl groups. These coatingcompositions are used as primers and are optimized for adhesion tometallic substrates, especially aluminum substrates. Over these coatingcompositions, as part of an OEM finish or a refinish, it is possible toapply basecoat/clearcoat systems. In terms of scratch resistance andweathering stability, the coating compositions of WO 01/98393 are notoptimized. No mention is made of the quantitative conversion of thesilane groups and/or of the isocyanate groups during the crosslinkingreaction.

EP-A-0 994 117 describes moisture-curable mixtures comprising a polyolcomponent and a polyisocyanate component which may partly have beenreacted with a monoalkoxysilylalkylamine that has undergone reactionpreferably to an aspartate. Although coatings formed from such mixturesdo have a certain hardness, they are nevertheless of only limitedsuitability for OEM applications in terms of their weathering stabilityand, in particular, their scratch resistance.

US-A-2006/0217472 describes coating compositions which can comprise ahydroxy-functional acrylate, a low molecular mass polyol component, apolyisocyanate, and an amino-functional alkoxysilyl component,preferably bisalkoxysilylamine. Such coating compositions are used asclearcoat material in basecoat/clearcoat systems and lead toscratchproof coatings. However, they have only very limited storagequalities, and the resulting coatings have low weathering stability,particularly with respect to UV radiation in a wet/dry cycle.

WO 2006/042585 describes clearcoat materials which are suitable for OEMfinishing and which as their main binder component comprisepolyisocyanates whose isocyanate groups, preferably to an extent of morethan 90 mol %, have undergone reaction with bisalkoxysilylamines.Clearcoat materials of this kind combine excellent scratch resistancewith high chemical and weathering resistance. But there is still a needfor a further improvement in the weathering stability, particularly withrespect to cracking under UV irradiation in a wet/dry cycle, withretention of the high level of scratch proofing.

EP-A-1 273 640 describes 2K coating compositions composed of a polyolcomponent and of a crosslinker component consisting of aliphatic and/orcycloaliphatic polyisocyanates, 0.1 to 95 mol % of the free isocyanategroups originally present having undergone reaction withbisalkoxysilylamine. These coating compositions can be used for OEMfinishing and when fully cured combine good scratch resistance witheffective resistance to environmental influences. Nevertheless, thesecoating compositions have a particularly strong propensity towardaftercrosslinking, with the consequence—directly after thermal curing tocompletion—of inadequate scratch resistance of the coatings. Thesignificant after crosslinking likewise impacts adversely on theweathering stability, since there is an increased risk of stress cracks.

The above-described coating materials which, through the use oforganofunctional silanes, include both organic and inorganicconstituents are also referred to as organic-inorganic coatingmaterials. Depending on the formulation used it is possible to producesurfaces of extreme scratch resistance.

It is known in the literature that crosslinking reactions can beaccelerated by means of very different catalysts. Whereas tertiaryamines or certain metal catalysts are more particularly suitable ascatalysts for isocyanate crosslinking (see inter alia M. Dahm, K. Uhlig,Kunststoff handbook 7, page 92 ff.) the silane condensation reactionsare catalyzed using, more particularly, acids, including, specifically,blocked partial esters of phosphoric acid. In organic-inorganic hybridsystems of this kind there may be unwanted interactions between theparticular catalysts used, since certain catalysts on the one handaccelerate one reaction and in certain circumstances inhibit the otherreaction that is progressing simultaneously. It is necessary,furthermore, to take account of aspects of the environmentalcompatibility of catalysts. For instance, inter alia, the use of tincatalysts is only a very limited possibility in practice, since theeffect of these materials on the human body is very toxic. Experimentalinvestigations have shown that the use of an individual catalyst isgenerally not sufficient to accelerate both crosslinking reactionscorrespondingly. In practice, this frequently leads to a situation inwhich comparatively low conversion rates are observed, at least in thecase of one of the crosslinking reactions: for example, only about 20%in the isocyanate reaction.

It was an object of the present invention to provide coatingcompositions, particularly for the clearcoat film in OEM finishes andautomotive refinishes, that lead to a network with a high degree ofweathering stability, the unwanted formation of moieties unstable tohydrolysis and weathering being very largely suppressed, in order toensure high acid resistance. In addition, the coating compositions oughtto lead to coatings which have a high degree of scratchproofing directlyafter thermal curing, and in particular a high retention of gloss afterscratch exposure. Moreover, the coatings and coating systems, especiallythe clearcoat systems, ought to be able to be produced even in filmthicknesses >40 μm without stress cracks occurring. This is a keyrequirement for the use of the coatings and coating systems,particularly of the clearcoat systems, in the technologically andesthetically particularly demanding field of automotive OEM finishing.

The intention in particular was to provide clearcoat systems featuringhigh resistance, particularly to cracking, under weathering with UVradiation in a wet/dry cycle, in combination with outstandingscratchproofing.

Furthermore, the new coating compositions ought to be preparable easilyand with very good reproducibility, and ought not to present anyenvironmental problems during application of the coating material.

A key problem facing the present invention is to achieve as completecrosslinking as possible for both reactions for coating materials whichare cured by hydrolysis of alkoxysilane compounds and, additionally, bythe reaction of isocyanate groups with hydroxyl groups. In particularthe isocyanate conversion is to be increased, without the silanecrosslinking being adversely affected. Surprisingly it has been foundthat this problem can be solved through the use of bicyclic amines forblocking phosphoric acid catalysts.

SUMMARY OF THE INVENTION

The present invention accordingly provides coating compositions, of thetype specified at the outset, wherein the catalyst (D) is a bicyclicamine.

In light of the prior art it was surprising and unforeseeable for theskilled worker that the objects on which the present invention was basedcould be achieved by means of the coating composition of the invention.

The components of the invention can be prepared particularly easily andwith very good reproducibility, and do not cause any significanttoxicological or environmental problems during application of thecoating material.

Advantageous embodiments of the present invention will become apparentfrom the dependent claims.

The coating compositions of the invention produce new coatings andcoating systems, especially clearcoat systems, which are highlyscratchproof and, in contrast to common, highly crosslinked scratchproofsystems, are acid-resistant. Moreover, the coatings and coating systemsof the invention, especially the clearcoat systems, can be produced evenin film thicknesses >40 μm without stress cracks occurring. Consequentlythe coatings and coating systems of the invention, especially theclearcoat systems, can be used in the technologically and estheticallyparticularly demanding field of automotive OEM finishing. In thatcontext they are distinguished by particularly high carwash resistanceand scratch resistance. In particular, the coatings possess their higherscratch resistance directly after the curing of the coatings tocompletion, thereby allowing the coatings to be handled with no problemsdirectly following the curing to completion. The resistance of thecoatings of the invention to cracking under UV radiation and wet/drycycling in the CAM180 test (to DIN EN ISO 11341 February 98 and DIN ENISO 4892-2 November 00), moreover, in combination with a high scratchresistance, is outstanding.

It is assumed that the above-described advantageous properties are to beattributed to the full progression of the simultaneously occurringcrosslinking reactions.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

Catalysts comprising phosphorus and nitrogen are used as catalysts (C)for the silane crosslinking. In this case, mixtures of two or moredifferent catalysts (C) can also be used.

Examples of suitable phosphorus catalysts (C) are substituted phosphonicdiesters and diphosphonic diesters, preferably from the group consistingof acyclic phosphonic diesters, cyclic phosphonic diesters, acyclicdiphosphonic diesters, and cyclic diphosphonic diesters. Catalysts ofthis kind are described for example in the German patent applicationDE-A-102005045228.

Use is made more particularly as catalyst (C), however, of substitutedphosphoric monoesters and phosphoric diesters, preferably from the groupconsisting of acyclic phosphoric diesters and cyclic phosphoricdiesters, more preferably amine adducts of the phosphoric monoesters anddiesters.

The acyclic phosphoric diesters (C) are selected more particularly fromthe group consisting of acyclic phosphoric diesters (C) of the generalformula (IV):

where the radicals R₁₀ and R₁₁ are selected from the group consistingof:

-   -   substituted and unsubstituted alkyl- having 1 to 20, preferably        2 to 16, and more particularly 2 to 10 carbon atoms, cycloalkyl-        having 3 to 20, preferably 3 to 16, and more particularly 3 to        10 carbon atoms, and aryl- having 5 to 20, preferably 6 to 14,        and more particularly 6 to 10 carbon atoms,    -   substituted and unsubstituted alkylaryl-, arylalkyl-,        alkylcycloalkyl-, cycloalkylalkyl-, arylcycloalkyl-,        cycloalkylaryl-, alkylcycloalkylaryl-, alkylarylcycloalkyl-,        arylcycloalkylalkyl-, arylalkylcycloalkyl-,        cycloalkylalkylaryl-, and cycloalkylarylalkyl-, the alkyl,        cycloalkyl-, and aryl groups present therein in each case        containing the above-recited number of carbon atoms; and    -   substituted and unsubstituted radical- of the above-recited        kind, containing at least one, more particularly one, heteroatom        selected from the group consisting of oxygen atom, sulfur atom,        nitrogen atom, phosphorus atom, and silicon atom, more        particularly oxygen atom, sulfur atom, and nitrogen atom; and        additionally also being able to represent hydrogen (partial        esterification).

The catalysts (C) are used preferably in fractions of 0.01 to 20% byweight, more preferably in fractions of 0.1 to 10% by weight, based onthe nonvolatile constituents of the coating composition of theinvention.

Examples of suitable catalysts (D) are 1,5-diazabicyclo[4.3.0]non-5-eneor 1,8-diazabicyclo[5.4.0]undec-7-ene.

The catalysts are used preferably in fractions of 0.01 to 20% by weight,more preferably in fractions of 0.1 to 10% by weight, based on thenonvolatile constituents of the coating composition of the invention. Inthis context, the amount of catalyst used also has a certain influenceon the crosslinking, since a relatively low level of activity on thepart of the catalyst can be partially compensated by means ofcorrespondingly higher amounts employed.

The Structural Units Having Hydrolyzable Silane Groups

It is essential to the invention that one or more constituents of thecoating composition contain hydrolyzable silane groups. Particularlysuitable in this context are coating compositions wherein one or moreconstituents of the coating composition at least partly contain one ormore, alike or different structural units of the formula (I)—X—Si—R″_(x)G_(3-x)  (I)with

-   G=identical or different hydrolyzable groups,-   X=organic radical, more particularly linear and/or branched alkylene    or cycloalkylene radical having 1 to 20 carbon atoms, very    preferably-   X=alkylene radical having 1 to 4 carbon atoms,-   R″=alkyl, cycloalkyl, aryl, or aralkyl, it being possible for the    carbon chain to be interrupted by nonadjacent oxygen, sulfur or NRa    groups, with Ra=alkyl, cycloalkyl, aryl or aralkyl, preferably    R″=alkyl radical, more particularly having 1 to 6 C atoms,-   x=0 to 2, preferably 0 to 1, more preferably x=0.

The structure of these silane radicals as well affects the reactivityand hence also the very substantial reaction during the curing of thecoating, hence affecting the establishment of an extremely lowpost-crosslinking index (PCI).

With regard to the compatibility and the reactivity of the silanes it ispreferred to use silanes having 3 hydrolyzable groups, i.e., x=0.

The hydrolyzable groups G may be selected from the group of halogens,more particularly chlorine and bromine, from the group of alkoxy groups,from the group of alkylcarbonyl groups, and from the group of acyloxygroups. Particular preference is given to alkoxy groups (OR′).

The respective preferred alkoxy radicals (OR′) may be alike ordifferent; what is critical for the structure of the radicals, however,is to what extent they influence the reactivity of the hydrolyzablesilane groups. Preferably R′ is an alkyl radical, more particularlyhaving 1 to 6 C atoms.

Particularly preferred radicals R′ are those which increase thereactivity of the silane groups, i.e., represent good leaving groups. Tothis extent, a methoxy radical is preferred over an ethoxy radical,which is preferred in turn over a propoxy radical. With particularpreference R′=ethyl and/or methyl, more particularly methyl.

The reactivity of organofunctional silanes can also be significantlyinfluenced, furthermore, through the length of the spacers X betweensilane functionality and organic functional group serving for reactionwith the modifying constituent. As examples of this, mention may be madeof the “alpha” silanes, available from the company Wacker, in whichthere is a methylene group, instead of the propylene group present inthe case of “gamma” silanes, between Si atoms and functional group. Toillustrate this it is observed thatmethacryloyloxymethyltrimethoxysilane (“alpha” silane, e.g., commercialproduct GENIOSIL® XL 33 from Wacker) is used in preference overmethacryloyloxypropyltrimethoxysilane (“gamma” silane, e.g., commercialproduct GENIOSIL® GF 31 from Wacker) in order to introduce thehydrolyzable silane groups into the coating composition.

Very generally, spacers which increase the reactivity of the silanes arepreferred over spacers which lower the reactivity of the silanes.

In addition, the functionality of the silanes, as well, has an influenceon the post-crosslinking index. By functionality in this context ismeant the number of radicals of the formula (I) per molecule. The termmonofunctional silane therefore refers to silanes which per silanemolecule in each case introduce one radical of the formula (I) into theconstituent that is to be modified. The term difunctional silane refersto silanes which per silane molecule introduce in each case two radicalsof the formula (I) into the constituent.

Particular preference is given, in accordance with the invention, tocoating compositions wherein the constituents have been modified with amixture of a monofunctional silane and a difunctional silane.Difunctional silanes used in this context are more particularly thoseamino-functional disilanes of the formula (IIa) that are describedbelow, and monofunctional silanes used are more particularly thosesilanes of the formula (IIIa) that are described later on below.

Finally, it is also possible for nonfunctional substituents on theorganofunctional silane that is used to introduce the structural units(I) and/or (II) and/or (III) to influence the reactivity of thehydrolyzable silane group. This may be illustrated by way of exampletaking as an example bulky voluminous substituents on the aminefunction, which are able to reduce the reactivity of amine-functionalsilanes. Against this backgroundN-(n-butyl)-3-aminopropyltrimethoxysilane is preferred beforeN-cyclohexyl-3-aminopropyltrimethoxysilane for the introduction of thestructural units (III).

Very generally, the radicals which increase the reactivity of thesilanes are preferred over radicals which lower the reactivity of thesilanes.

The structural units of the formula (I) can be introduced into theconstituents of the coating composition in different ways. A featurecommon to the various ways, however, is that the introduction of thestructural units is accomplished via a reaction between the functionalgroups of the constituents it is intended to modify and complementaryfunctional groups of the silane. By way of example, therefore, variouspossibilities for introducing the structural units (I) into the compound(A) containing hydroxyl groups and, where appropriate, further reactivegroups as well, and/or into the compound (B) containing isocyanategroups, are set out below.

Use is made, more particularly in the context of Michael additions, of,for example, primary aminosilanes, such as 3-aminopropyltriethoxysilane(available for example under the brand name Geniosil® GF 93 from WackerChemie), 3-aminopropyltrimethoxysilane (available for example under thebrand name Geniosil® GF 96 from Wacker Chemie),N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (available for exampleunder the brand name Geniosil® GF 9 and also Geniosil® GF 91 from WackerChem ie), N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane (availablefor example, under the brand name Geniosil® GF 95 from Wacker Chemie),and the like.

Use is made, more particularly in the context of additions toisocyanate-functional compounds, of, for example, secondaryaminosilanes, such as, for example, bis-(2-trimethoxysilylethyl)amine,bis-(2-triethoxysilyl-ethyl)amine, bis(3-triethoxysilylpropyl)amine(available under the trade name Dynasylan® 1122 from Degussa),bis(3-trimethoxysilyl-propyl)amine (available under the trade nameDynasylan® 1124 from Degussa), bis(4-triethoxysilylbutyl)amine,N-(n-butyl)-3-aminopropyl-trimethoxysilane (available under the tradename Dynasylan® 1189 from Degussa),N-(n-butyl)-3-aminopropyltriethoxysilane,N-cyclohexyl-3-aminopropyltrimethoxysilane (available under the brandname Geniosil® GF 92 from Wacker Chemie),N-cyclohexyl-3-aminopropyltriethoxy-silane,N-cyclohexylaminomethylmethyldiethoxysilane (available from WackerChemie under the trade name Geniosil® XL 924),N-cyclo-hexylaminomethyltriethoxysilane (available from Wacker Chemieunder the trade name Geniosil® XL 926),N-phenylaminomethyl-trimethoxysilane (available from Wacker Chemie underthe trade name Geniosil® XL 973), and the like.

Epoxy-functional silanes can be used more particularly for addition tocompounds with carboxylic acid or anhydride functionality. Examples ofsuitable epoxy-functional silanes are3-glycidyloxypropyltrimethoxysilane (available from Degussa under thetrade name Dynasylan® GLYMO), 3-glycidyloxypropyltriethoxysilane(available from Degussa under the trade name Dynasylan® GLYEO), and thelike.

Anhydride—functional silanes can be employed more particularly foraddition to epoxy-functional compounds. An example that may be mentionedof a silane with anhydride functionality is3-(triethoxysilyl)propylsuccinic anhydride (available from Wacker Chemieunder the trade name Geniosil® GF 20).

Silanes of this kind can be used in the context of Michael reactions orelse in the context of metal-catalyzed reactions. Those exemplified are3-methacryloyloxypropyltrimethoxysilane (available for example fromDegussa under the trade name Dynasilan® MEMO, or from Wacker Chemieunder the trade name Geniosil® GF 31),3-methacryloyloxypropyltriethoxysilane, vinyltrimethoxysilane(available, among others, from Wacker Chemie under the trade nameGeniosil® XL 10), vinyldimethoxymethylsilane (available from, amongothers, Wacker Chemie under the trade name Geniosil® XL 12),vinyltriethoxysilane (available, among others, from Wacker Chemie underthe trade name Geniosil® GF 56),(methacryloyloxymethyl)methyldimethoxysilane (available, among others,from Wacker Chemie under the trade name Geniosil® XL 32),methacryloyloxymethyltrimethoxysilane (available, among others, fromWacker Chemie under the trade name Geniosil® XL 33),(methacryloyloxymethyl)methyldiethoxysilane (available, among others,from Wacker Chemie under the trade name Geniosil® XL 34),methacryloyloxymethyltriethoxysilane (available, among others, fromWacker Chemie under the trade name Geniosil® XL 36).

Silanes with isocyanate function or carbamate function are employed inparticular in the context of reactions with hydroxy-functionalcompounds. Examples of silanes with isocyanate function are described inWO 07/03857, for example.

Examples of suitable isocyanatoalkyltrialkoxysilanes areisocyanato-propyltrimethoxysilane,isocyanatopropylmethyldimethoxysilane,isocyanatopropylmethyldiethoxysilane, isocyanatopropyltriethoxysilane,isocyanatopropyltriisopropoxysilane, isocyanatopropylmethyldiiso-propoxysilane, isocyanatoneohexyltrimethoxysilane,isocyanatoneo-hexyldimethoxysilane, isocyanatoneohexyldiethoxysilane,isocyanato-neohexyltriethoxysilane,isocyanatoneohexyltriisopropoxysilane,isocyanatoneohexyldiisopropoxysilane,isocyanatoisoamyltrimethoxy-silane,isocyanatoisoamylmethyldimethoxysilane,isocyanatoisoamyl-methyldiethoxysilane,isocyanatoisoamyltriethoxysilane, isocyanato-isoamyltriisopropoxysilaneand isocyanatoisoamylmethyldiisopropoxy-silane. Many isocyanatoalkyltri-and -di-alkoxysilanes are available commercially, for example, under thedesignation SILQUEST® from OSi Specialties, Inc., a Witco Corporationcompany.

The isocyanatopropylalkoxysilane used preferably has a high degree ofpurity, more particularly a purity of at least 95%, and is preferablyfree from additives, such as transesterification catalysts, which canlead to unwanted side reactions.

Use is made in particular of (isocyanatomethyl)methyldimethoxysilane(available from Wacker-Chemie under the brand name Geniosil® XL 42),3-isocyanatopropyltrimethoxysilane (available from Wacker-Chemie underthe brand name Geniosil® XL 40), and N-dimethoxy(methyl)silylmethylO-methylcarbamate (available from Wacker—Chemie under the brand nameGeniosil® XL 65).

More particular preference is given in accordance with the invention tocoating compositions comprising at least one hydroxyl-containingcompound (A) and at least one isocyanato-containing compound (B),wherein one or more constituents of the coating composition contain, asadditional functional components, between

2.5 and 97.5 mol %, based on the entirety of structural units (II) and(III), of at least one structural unit of the formula (II)—N(X—SiR″x(OR′)3-x)n(X′—SiR″y(OR′)3-y)m  (II)where

-   R′=hydrogen, alkyl or cycloalkyl, it being possible for the carbon    chain to be interrupted by nonadjacent oxygen, sulfur or NRa groups,    with Ra=alkyl, cycloalkyl, aryl or aralkyl, preferably R′=ethyl    and/or methyl,-   X, X′=linear and/or branched alkylene or cycloalkylene radical    having 1 to 20 carbon atoms, preferably X, X′=alkylene radical    having 1 to 4 carbon atoms,-   R″=alkyl, cycloalkyl, aryl or aralkyl, it being possible for the    carbon chain to be interrupted by nonadjacent oxygen, sulfur or NRa    groups, with Ra=alkyl, cycloalkyl, aryl or aralkyl, preferably    R″=alkyl radical, more particularly having 1 to 6 C atoms,-   n=0 to 2, m=0 to 2, m+n=2, and x,y=0 to 2,    and-   between 2.5 and 97.5 mol %, based on the entirety of structural    units (II) and (III), of at least one structural unit of the formula    (III)    —Z—(X—SiR″x(OR′)3-x)  (III),    where-   Z=—NH—, —NR—, —O—, with-   R=alkyl, cycloalkyl, aryl or aralkyl, it being possible for the    carbon chain to be interrupted by nonadjacent oxygen, sulfur or NRa    groups, with Ra=alkyl, cycloalkyl, aryl or aralkyl.-   x=0 to 2, and-   X, R′, R″ being as defined for formula (II).

Very particular preference is given to coating compositions wherein oneor more constituents of the coating composition contain between 5 and 95mol %, more particularly between 10 and 90 mol %, with particularpreference between 20 and 80 mol %, and very particularly between 30 and70 mol %, based in each case on the entirety of structural units (II)and (III), of at least one structural unit of the formula (II) andbetween 5 and 95 mol %, more particularly between 10 and 90 mol %, withparticular preference between 20 and 80 mol %, and very particularlybetween 30 and 70 mol %, based in each case on the entirety ofstructural unit (II) and (III), of at least one structural unit of theformula (III).

The Hydroxyl-Containing Compound (A)

As hydroxyl-containing compound (A) it is preferred to use low molecularmass polyols and also oligomeric and/or polymeric polyols.

Low molecular mass polyols used are, for example, diols, such as,preferably, ethylene glycol, neopentyl glycol, 1,2-propanediol,2,2-dimethyl-1,3-propanediol, 1,4-butanediol, 1,3-butanediol,1,5-pentane-diol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol,1,4-cyclohexane-dimethanol, and 1,2-cyclohexanedimethanol, and alsopolyols, such as, preferably, trimethylolethane, trimethylolpropane,trimethylolhexane, 1,2,4-butanetriol, pentaerythritol, anddipentaerythritol.

Low molecular mass polyols of this kind are preferably admixed in minorproportions to the oligomeric and/or polymeric polyol component (A).

The preferred oligomeric and/or polymeric polyols (A) have mass-averagemolecular weights Mw>500 daltons, as measured by means of GPC (gelpermeation chromatography), preferably between 800 and 100 000 daltons,in particular between 1000 and 50 000 daltons. Particularly preferredare polyester polyols, polyurethane polyols, polysiloxane polyols, and,in particular, polyacrylate polyols and/or polymethacrylate polyols, andtheir copolymers, referred to as polyacrylate polyols below. The polyolspreferably have an OH number of 30 to 400 mg KOH/g, in particularbetween 100 and 300 KOH/g. The glass transition temperatures, asmeasured by DSC (differential thermal analysis), of the polyols arepreferably between −150 and 100° C., more preferably between −120° C.and 80° C.

Suitable polyester polyols are described for example in EP-A-0 994 117and EP-A-1 273 640. Polyurethane polyols are prepared preferably byreacting polyester polyol prepolymers with suitable di- orpolyisocyanates and are described in EP-A-1 273 640, for example.

Suitable polysiloxane polyols are described for example inWO-A-01/09260, and the polysiloxane polyols recited therein can beemployed preferably in combination with further polyols, especiallythose having relatively high glass transition temperatures.

The polyacrylate polyols that are very particularly preferred inaccordance with the invention are generally copolymers and preferablyhave mass-average molecular weights Mw of between 1000 and 20 000daltons, in particular between 1500 and 10 000 daltons, measured in eachcase by means of gel permeation chromatography (GPC) against apolystyrene standard. The glass transition temperature of the copolymersis generally between −100 and 100° C., in particular between −50 and 80°C. (measured by means of DSC measurements). The polyacrylate polyolspreferably have an OH number of 60 to 250 mg KOH/g, in particularbetween 70 and 200 KOH/g, and an acid number of between 0 and 30 mgKOH/g.

The hydroxyl number (OH number) indicates how many mg of potassiumhydroxide are equivalent to the amount of acetic acid bound by 1 g ofsubstance during acetylation. For the determination, the sample isboiled with acetic anhydride-pyridine and the acid formed is titratedwith potassium hydroxide solution (DIN 53240-2). The acid number hereindicates the number of mg of potassium hydroxide consumed inneutralizing 1 g of the respective compound of component (b) (DIN EN ISO2114).

Hydroxyl-containing monomer units used are preferably hydroxyalkylacrylates and/or hydroxyalkyl methacrylates, such as, in particular,2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropylacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate,3-hydroxypropyl methacrylate, 3-hydroxybutyl acrylate, 3-hydroxybutylmethacrylate, and, in particular, 4-hydroxybutyl acrylate and/or4-hydroxybutyl methacrylate.

Further monomer units used for the polyacrylate polyols are preferablyalkyl methacrylates and/or alkyl methacrylates, such as, preferably,ethyl acrylate, ethyl methacrylate, propyl acrylate, propylmethacrylate, isopropyl acrylate, isopropyl methacrylate, butylacrylate, butyl methacrylate, isobutyl acrylate, isobutyl methacrylate,tert-butyl acrylate, tert-butyl methacrylate, amyl acrylate, amylmethacrylate, hexyl acrylate, hexyl methacrylate, ethylhexyl acrylate,ethylhexyl methacrylate, 3,3,5-trimethylhexyl acrylate,3,3,5-trimethylhexyl methacrylate, stearyl acrylate, stearylmethacrylate, lauryl acrylate or lauryl methacrylate, cycloalkylacrylates and/or cycloalkyl methacrylates, such as cyclopentyl acrylate,cyclopentyl methacrylate, isobornyl acrylate, isobornyl methacrylate,or, in particular, cyclohexyl acrylate and/or cyclohexyl methacrylate.

Further monomer units which can be used for the polyacrylate polyols arevinylaromatic hydrocarbons, such as vinyltoluene, alpha-methylstyreneor, in particular, styrene, amides or nitriles of acrylic or methacrylicacid, vinyl esters or vinyl ethers, and, in minor amounts, inparticular, acrylic and/or methacrylic acid.

In a further embodiment of the invention the hydroxyl-containingcompound A as well as the hydroxyl groups comprises structural units ofthe formula (I) and/or of the formula (II) and/or of the formula (III).

Structural units of the formula (II) can be introduced into the compound(A) by incorporation of monomer units containing such structural units,or by reaction of polyols containing further functional groups with acompound of the formula (IIa)HN(X—SiR″x(OR′)3-x)n(X′—SiR″y(OR′)3-y)m  (IIa),where the substituents are as defined above. For the reaction of thepolyol with the compound (IIa), the polyol, correspondingly, has furtherfunctional groups which react with the secondary amino group of thecompound (IIa), such as acid or epoxy groups in particular. Inventivelypreferred compounds (IIa) are bis(2-ethyltrimethoxysilyl)amine,bis(3-propyltrimethoxysilyl)amine, bis(4-butyltrimethoxysilyl)amine,bis(2-ethyltriethoxysilyl)amine, bis(3-propyltrimethoxysilyl)amineand/or bis(4-butyltriethoxysilyl)amine.Bis(3-propyltrimethoxysilyl)amine is especially preferred. Aminosilanesof this kind are available for example under the brand name DYNASILAN®from DEGUSSA or Siiquest® from OSI.

Monomer units which carry the structural elements (II) are preferablyreaction products of acrylic and/or methacrylic acid or ofepoxy-containing alkyl acrylates and/or methacrylates with theabove-mentioned compounds (IIa).

Structural units of the formula (III) can be introduced into thecompound (A) by incorporation of monomer units containing suchstructural units or by reaction of polyols containing further functionalgroups with a compound of the formula (IIIa)H—Z—(X—SiR″x(OR′)3-x)  (IIIa),where the substituents are as defined above. For the reaction of thepolyol with the compound (IIIa), the polyol, correspondingly, hasfurther functional groups which react with the functional group —ZH ofthe compound (IIIa), such as acid, epoxy or ester groups in particular.Inventively preferred compounds (IIIa) are omega-aminoalkyl- oromega-hydroxyalkyltrialkoxysilanes, such as, preferably,2-aminoethyltri-methoxysilane, 2-aminoethyltriethoxysilane,3-aminopropyltrimethoxy-silane, 3-aminopropyltriethoxysilane,4-aminobutyltrimethoxysilane, 4-aminobutyltriethoxysilane,2-hydroxyethyltrimethoxysilane, 2-hydroxy-ethyltriethoxysilane,3-hydroxypropyltrimethoxysilane, 3-hydroxypropyl-triethoxysilane,4-hydroxybutyltrimethoxysilane, and 4-hydroxybutyl-triethoxysilane.Particularly preferred compounds (IIa) areN-(2-(tri-methoxysilyl)-ethyl)alkylamines,N-(3-(trimethoxysilyl)propyl)alkyl-amines,N-(4-(trimethoxysilyl)butyl)alkylamines,N-(2-(triethoxy-silyl)ethyl)alkylamines,N-(3-(triethoxysilyl)propyl)alkylamines and/orN-(4-(triethoxysilyl)butyl) alkylamines.N-(3-(Trimethoxysilyl)propyl)butyl-amine is especially preferred.Aminosilanes of this kind are available for example under the brand nameDYNASILAN® from DEGUSSA or Silquest® from OSI.

Monomer units which carry the structural elements (III) are preferablyreaction products of acrylic and/or methacrylic acid or ofepoxy-containing alkyl acrylates and/or methacrylates, and also, in thecase of hydroxy-functional alkoxysilyl compounds, transesterificationproducts of alkyl acrylates and/or methacrylates, especially with theabove-mentioned hydroxy- and/or amino-functional alkoxysilyl compounds(IIIa).

The Isocyanate-Containing Compounds (B)

As component (B), the coating compositions of the invention comprise oneor more compounds having free, i.e., unblocked, and/or blockedisocyanate groups. Preferably the coating compositions of the inventioncomprise compounds (B) having free isocyanate groups. The freeisocyanate groups of the isocyanato-containing compounds B may also,however, be used in blocked form. This is preferably the case when thecoating compositions of the invention are used as one-component systems.

The di- and/or polyisocyanates which serve as core structures for theisocyanato-containing compounds (B) used with preference in accordancewith the invention are preferably conventional substituted orunsubstituted aromatic, aliphatic, cycloaliphatic and/or heterocyclicpolyisocyanates. Examples of preferred polyisocyanates are as follows:2,4-toluene diisocyanate, 2,6-toluene diisocyanate, diphenylmethane4,4′-diisocyanate, diphenylmethane 2,4′-diisocyanate, p-phenylenediisocyanate, biphenyl diisocyanates, 3,3′-dimethyl-4,4′-diphenylenediisocyanate, tetramethylene 1,4-diisocyanate, hexamethylene1,6-diisocyanate, 2,2,4-trimethylhexane 1,6-diisocyanate, isophoronediisocyanate, ethylene diisocyanate, 1,12-dodecane diisocyanate,cyclobutane 1,3-diisocyanate, cyclohexane 1,3-diisocyanate, cyclohexane1,4-diisocyanate, methylcyclohexyl diisocyanates, hexahydrotoluene2,4-diisocyanate, hexahydrotoluene 2,6-diisocyanate, hexahydrophenylene1,3-diisocyanate, hexahydrophenylene 1,4-diisocyanate,perhydrodiphenylmethane 2,4′-diisocyanate, 4,4′-methylenedicyclohexyldiisocyanate (e.g., Desmodur® W from Bayer AG), tetramethylxylyldiisocyanates (e.g., TMXDI® from American Cyanamid), and mixtures of theaforementioned polyisocyanates. Additionally preferred polyisocyanatesare the biuret dimers and the isocyanurate trimers of the aforementioneddiisocyanates.

Particularly preferred polyisocyanates are hexamethylene1,6-diisocyanate, isophorone diisocyanate, and4,4′-methylenedicyclohexyl diisocyanate, their biuret dimers and/orisocyanurate trimers.

In a further embodiment of the invention the polyisocyanates arepolyisocyanate prepolymers containing urethane structural units whichare obtained by reacting polyols with a stoichiometric excess ofaforementioned polyisocyanates. Polyisocyanate prepolymers of this kindare described for example in U.S. Pat. No. 4,598,131.

The isocyanato-containing compounds (B) that are especially preferred inaccordance with the invention, functionalized with the structural units(II) and (III), are prepared with preference by reacting theaforementioned di- and/or polyisocyanates with the aforementionedcompounds (IIa) and (IIIa), by reacting

between 2.5 and 90 mol %, preferably 5 to 85 mol %, more preferably 7.5to 80 mol %, of the isocyanate groups in the core polyisocyanatestructure with at least one compound (IIa) and

between 2.5 and 90 mol %, preferably 5 to 85 mol %, more preferably 7.5to 80 mol %, of the isocyanate groups in the core polyisocyanatestructure with at least one compound (IIIa).

The total fraction of the isocyanate groups reacted with the compounds(IIa) and (IIIa) in the polyisocyanate compound (B) is between 5 and 95mol %, preferably between 10 and 90 mol %, more preferably between 15and 85 mol % of the isocyanate groups in the core polyisocyanatestructure. Particularly in the case of a high degree of silanization,i.e., when a high proportion of the isocyanate groups, more particularlyat least 50 mol %, having been reacted with the compounds (IIa)/(IIIa),the isocyanate groups are reacted advantageously with a mixture of thecompounds (IIa) and (IIIa).

Particularly preferred compounds (IIa) arebis(2-ethyltrimethoxy-silyl)amine, bis(3-propyltrimethoxysilyl)amine,bis(4-butyltrimethoxy-silyl)amine, bis(2-ethyltriethoxysilyl)amine,bis(3-propyltrimethoxy-silyl)amine and/orbis(4-butyltriethoxysilyl)amine. Bis(3-propyltrimethoxy-silyl)amine isespecially preferred. Aminosilanes of this kind are available forexample under the brand name DYNASILAN® from DEGUSSA or Silquest® fromOSI.

Preferred compounds (IIIa) are 2-aminoethyltrimethoxysilane,2-aminoethyltriethoxsilane, 3-aminopropyltrimethoxysilane,3-amino-propyltriethoxysilane, 4-aminobutyltrimethoxysilane,4-aminobutyltri-ethoxysilane, 2-hydroxyethyltrimethoxysilane,2-hydroxyethyltriethoxy-silane, 3-hydroxypropyltrimethoxysilane,3-hydroxypropyltriethoxysilane, 4-hydroxybutyltrimethoxysilane, and4-hydroxybutyltriethoxysilane.

Particularly preferred compounds (IIIa) areN-(2-(tri-methoxysilyl)ethyl)alkylamines,N-(3-(trimethoxysilyl)propyl)alkylamines,N-(4-(trimethoxysilyl)butyl)alkylamines,N-(2-(triethoxysilyl)ethyl)alkyl-amines,N-(3-(triethoxysilyl)propyl)alkylamines and/orN-(4-(triethoxy-silyl)butyl)alkylamines.N-(3-(Trimethoxysilyl)propyl)butylamine is especially preferred.Aminosilanes of this kind are available for example under the brand nameDYNASILAN® from DEGUSSA or Silquest® from OSI.

Especially preferred isocyanato-containing compounds (B) are reactionproducts of hexamethylene 1,6-diisocyanate and/or isophoronediisocyanate, and/or their isocyanurate trimers, withbis(3-propyltrimethoxysilyl)amine andN-(3-(trimethoxysilyl)propyl)butylamine. The reaction of theisocyanato-containing compounds (B) with the compounds (IIa) and (IIIa)takes place preferably in inert gas at temperatures of not more than100° C., preferably of not more than 60° C.

The free isocyanate groups of the isocyanato-containing compounds B canalso be used in blocked form. This is preferably the case when thecoating compositions of the invention are used as one-component systems.For the purpose of blocking it is possible in principle to use anyblocking agent which can be used for blocking polyisocyanates and whichhas a sufficiently low unblocking temperature. Blocking agents of thiskind are very familiar to the skilled worker. It is preferred to useblocking agents as described in EP-A-0 626 888 and EP-A-0 692 007.

The Combination of Components A and B, and Further Components of theCoating Composition

The weight fraction of hydroxyl-containing compounds A to be employed,based on the weight fraction of the isocyanato-containing compounds B,is dependent on the hydroxy equivalent weight of the polyol and on theequivalent weight of the free isocyanate groups of the polyisocyanate B.

It is preferred that, in the coating composition of the invention, oneor more constituents contain between 2.5 to 97.5 mol %, based on the sumof structural units (II) and (III), of at least one structural unit (II)and between 2.5 to 97.5 mol %, based on the sum of structural units (II)and (III), of at least one structural unit (III).

The coating compositions of the invention contain preferably between2.5% and 97.5%, more preferably between 5% and 95%, very preferablybetween 10% and 90%, and in particular between 20% and 80%, by weight,based on the amount of nonvolatile substances in the coatingcomposition, of the hydroxyl-containing compounds (A), and preferablybetween 2.5% and 97.5%, more preferably between 5% and 95%, verypreferably between 10% and 90%, and in particular between 20% and 80%,by weight, based on the amount of nonvolatile substances in the coatingcomposition, of the isocyanato-containing compounds (B).

Based on the sum of the functional groups critical for crosslinking inthe coating composition of the invention, formed from the fractions ofthe hydroxyl and isocyanate groups and also the fractions of thestructural elements (I) and/or (II) and/or (III), the structuralelements (I) and/or (II) and/or (III) are present preferably infractions of 2.5 to 97.5 mol %, more preferably between 5 and 95 mol %,and very preferably between 10 and 90 mol %.

In a further embodiment of the invention the structural elements (I),(II) and/or (III) may additionally also be part of one or more furthercomponents (E), different than the components (A) and (B), in which casethe criteria to be applied are those specified above. By way of exampleit is possible as component (E) to use oligomers or polymers containingalkoxysilyl groups, such as, for example, the poly(meth)acrylatesspecified in patents and patent applications U.S. Pat. Nos. 4,499,150,4,499,151 or EP-A-0 571 073, as carriers of structural elements (III),or to use the compounds specified in WO-A-2006/042585, as carriers ofstructural elements (II). Generally speaking, components (E) of thiskind are used in fractions of up to 40%, preferably up to 30%, morepreferably up to 25%, by weight, based on the nonvolatile constituentsof the coating composition.

The weight fractions of the polyol A and of the polyisocyanate B arepreferably selected such that the molar equivalent ratio of theunreacted isocyanate groups of the isocyanate-containing compounds (B)to the hydroxyl groups of the hydroxyl-containing compounds (A) isbetween 0.9:1 and 1:1.1, preferably between 0.95:1 and 1.05:1, morepreferably between 0.98:1 and 1.02:1.

Where the compositions are one-component coating compositions, aselection is made of the isocyanato-containing compounds (B) whose freeisocyanate groups have been blocked with the blocking agents describedabove.

In the case of the inventively preferred 2-component (2K) coatingcompositions, a coating component comprising the hydroxyl-containingcompound (A) and also further components, described below, is mixedconventionally with a further coating component, comprising theisocyanato-containing compound (B) and, where appropriate, further ofthe components described below, this mixing taking place shortly beforethe coating composition is applied; generally speaking, the coatingcomponent that comprises the compound (A) comprises the catalyst andalso part of the solvent.

Solvents suitable for the coating compositions of the invention are inparticular those which, in the coating composition, are chemically inerttoward the compounds (A) and (B) and also do not react with (A) and (B)when the coating composition is being cured. Examples of such solventsare aliphatic and/or aromatic hydrocarbons such as toluene, xylene,solvent naphtha, Solvesso 100 or Hydrosol® (from ARAL), ketones, such asacetone, methyl ethyl ketone or methyl amyl ketone, esters, such asethyl acetate, butyl acetate, pentyl acetate or ethyl ethoxypropionate,ethers, or mixtures of the aforementioned solvents. The aprotic solventsor solvent mixtures preferably have a water content of not more than 1%,more preferably not more than 0.5%, by weight, based on the solvent.

Besides the compounds (A), (B), and (D) it is possible additionally touse further binders (F), which preferably are able to react and formnetwork points with the hydroxyl groups of the compound (A) and/or withthe free isocyanate groups of the compound (B) and/or with thealkoxysilyl groups of the compounds (A), (B) and/or (D).

By way of example it is possible to use amino resins and/or epoxy resinsas component (F). Suitable amino resins are the typical, known aminoresins, some of whose methylol and/or methoxymethyl groups may have beendefunctionalized by means of carbamate or allophanate groups.Crosslinking agents of this kind are described in patents U.S. Pat. No.4,710,542 and EP-B-0 245 700 and also in the article by B. Singh andcoworkers, “Carbamylmethylated Melamines, Novel Crosslinkers for theCoatings Industry” in Advanced Organic Coatings Science and TechnologySeries, 1991, Volume 13, pages 193 to 207.

Generally speaking, such components (F) are used in fractions of up to40%, preferably up to 30%, more preferably up to 25%, by weight, basedon the nonvolatile constituents of the coating composition.

The coating composition of the invention may further comprise at leastone typical, known coatings additive in effective amounts, i.e. inamounts preferably up to 30%, more preferably up to 25%, and inparticular up to 20% by weight, in each case based on the nonvolatileconstituents of the coating composition.

Examples of suitable coatings additives are:

-   -   particularly UV absorbers;    -   particularly light stabilizers such as HALS compounds,        benzotriazoles or oxalanilides;    -   free-radical scavengers;    -   slip additives;    -   polymerization inhibitors;    -   defoamers;    -   reactive diluents, of the kind which are common knowledge from        the prior art, and which are preferably inert toward the        —Si(OR)₃ groups;    -   wetting agents such as siloxanes, fluorine compounds, carboxylic        monoesters, phosphoric esters, polyacrylic acids and their        copolymers, or polyurethanes;    -   adhesion promoters such as tricyclodecanedimethanol;    -   flow control agents;    -   film-forming assistants such as cellulose derivatives;    -   fillers such as, for example, nanoparticles based on silicon        dioxide, aluminum oxide or zirconium oxide; for further details        refer to Römpp Lexikon “Lacke and Druckfarben” Georg Thieme        Verlag, Stuttgart, 1998, pages 250 to 252;    -   rheology control additives, such as the additives known from        patents WO 94/22968, EP-A-0 276 501, EP-A-0 249 201 or WO        97/12945; crosslinked polymeric microparticles, as disclosed for        example in EP-A-0 008 127; inorganic phyllosilicates such as        aluminum-magnesium silicates, sodium-magnesium, and        sodium-magnesium-fluorine-lithium phyllosilicates of the        montmorillonite type; silicas such as Aerosils; or synthetic        polymers containing ionic and/or associative groups such as        polyvinyl alcohol, poly(meth)acrylamide, poly(meth)acrylic acid,        polyvinylpyrrolidone, styrene-maleic anhydride copolymers or        ethylene-maleic anhydride copolymers and their derivatives, or        hydrophobically modified ethoxylated urethanes or polyacrylates;    -   and/or flame retardants.

In a further embodiment of the invention the coating composition of theinvention may additionally comprise further pigments and/or fillers andmay serve for producing pigmented topcoats. The pigments and/or fillersemployed for this purpose are known to the skilled worker.

Because the coatings of the invention produced from the coatingcompositions of the invention adhere excellently even to electrocoats,surfacer coats, basecoat systems or typical, known clearcoat systemsthat have already cured, they are outstandingly suitable not only foruse in automotive OEM finishing but also for automotive refinish or forthe modular scratchproofing of automobile bodies that have already beenpainted.

The coating compositions of the invention can be applied by any of thetypical application methods, such as spraying, knife coating, spreading,pouring, dipping, impregnating, trickling or rolling, for example. Inthe course of such application, the substrate to be coated may itself beat rest, with the application equipment or unit being moved.Alternatively the substrate to be coated, in particular a coil, may bemoved, with the application unit at rest relative to the substrate orbeing moved appropriately.

Preference is given to employing spray application methods, such ascompressed-air spraying, airless spraying, high-speed rotation,electrostatic spray application (ESTA), alone or in conjunction with hotspray application such as hot-air spraying, for example.

The applied coating compositions of the invention can be cured after acertain rest time. The rest time serves, for example, for the levelingand devolatilization of the coating films or for the evaporation ofvolatile constituents such as solvents. The rest time may be assistedand/or shortened by the application of elevated temperatures and/or by areduced humidity, provided this does not entail any damage or alterationto the coating films, such as premature complete crosslinking, forinstance.

The thermal curing of the coating compositions has no peculiarities interms of method but instead takes place in accordance with the typical,known methods such as heating in a forced-air oven or irradiation withIR lamps. The thermal cure may also take place in stages. Anotherpreferred curing method is that of curing with near infrared (NIR)radiation.

The thermal cure takes place advantageously at a temperature of 30 to200° C., more preferably 40 to 190° C., and in particular 50 to 180° C.for a time of 1 min up to 10 h, more preferably 2 min up to 5 h, and inparticular 3 min to 3 h, although longer cure times may be employed inthe case of the temperatures that are employed for automotive refinish,which are preferably between 30 and 90° C.

The coating compositions of the invention produce new cured coatings,especially coating systems, more particularly clearcoat systems;moldings, especially optical moldings; and self-supporting films, all ofwhich are highly scratchproof and in particular are stable to chemicalsand to weathering. The coatings and coating systems of the invention,especially the clearcoat systems, can in particular be produced even infilm thicknesses >40 μm without stress cracks occurring.

For these reasons the coating compositions of the invention are ofexcellent suitability as decorative, protective and/or effect-imparting,highly scratchproof coatings and coating systems on bodies of means oftransport (especially motor vehicles, such as motor cycles, buses,trucks or automobiles) or parts thereof; on buildings, both interior andexterior; on furniture, windows, and doors; on plastics moldings,especially CDs and windows; on small industrial parts, on coils,containers, and packaging; on white goods; on films; on optical,electrical, and mechanical components; and on hollow glassware andarticles of everyday use.

The coating compositions and coating systems of the invention,especially the clearcoat systems, are employed in particular in thetechnologically and esthetically particularly demanding field ofautomotive OEM finishing and also of automotive refinish. Withparticular preference the coating compositions of the invention are usedin multistage coating methods, particularly in methods where a pigmentedbasecoat film is first applied to an uncoated or precoated substrate andthereafter a film with the coating compositions of the invention isapplied.

Not only water-thinnable basecoat materials but also basecoat materialsbased on organic solvents can be used. Suitable basecoat materials aredescribed for example in EP-A-0 692 007 and in the documents cited therein column 3 lines 50 et seq. The applied basecoat material is preferablyfirst dried, i.e., at least some of the organic solvent and/or water isstripped from the basecoat film in an evaporation phase. Drying isaccomplished preferably at temperatures from room temperature to 80° C.Drying is followed by the application of the coating composition of theinvention. Subsequently the two-coat system is baked, preferably underconditions employed for automotive OEM finishing, at temperatures from30 to 200° C., more preferably 40 to 190° C., and in particular 50 to180° C., for a time of 1 min up to 10 h, more preferably 2 min up to 5h, and in particular 3 min to 3 h, although longer cure times may alsobe employed at the temperatures employed for automotive refinish, whichare preferably between 30 and 90° C.

The coats produced with the coating composition of the invention arenotable in particular for an especially high chemical stability andweathering stability and also for a very good carwash resistance andscratchproofing, in particular for an excellent combination ofscratchproofing and weathering stability with respect to UV radiation ina wet/dry cycle.

In a further preferred embodiment of the invention, the coatingcomposition of the invention is used as a transparent clearcoat materialfor coating plastics substrates, especially transparent plasticssubstrates. In this case the coating compositions include UV absorbers,which in terms of amount and type are also designed for effective UVprotection of the plastics substrate. Here as well, the coatingcompositions are notable for an outstanding combination ofscratchproofing and weathering stability with respect to UV radiation ina wet/dry cycle. The plastics substrates thus coated are used preferablyas a substitute for glass components in automobile construction, theplastics substrates being composed preferably of polymethyl methacrylateor polycarbonate.

EXAMPLES Preparation Example 1 Preparation of the Partially SilanizedCuring Agent on the Basis of HDI Trimers

A reaction vessel was equipped with a condenser and charged withnitrogen. Subsequently the reaction vessel was charged with 57.3 partsby weight of trimerized isocyanate (Basonat® HI 100, available from BASFAG, Ludwigshafen) and 3.88 parts by weight of triethyl orthoformate. Ina separate vessel, 2.82 parts by weight ofN-(3-trimethoxysilylpropan-1-yl)-N-n-butylamine (Dynasilan® 1189 fromDegussa) were mixed with 36.89 parts by weight ofN,N-bis(3-trimethoxysilylpropan-1-yl)amine (Dynasilan® 1124 fromDegussa), with nitrogen blanketing. The resulting mixture of theamino-functional silanes was added slowly dropwise and with stirring tothe initial isocyanate charge, at a rate such that the reactiontemperature did not exceed 60° C. Following the addition, the reactionmixture was stirred at 60° C. until the titrimetrically determinedisocyanate content was 4.9%. At that point the mixture was cooled toroom temperature.

The solids (30 minutes, 130° C.) of the silanized isocyanate thusobtained was determined as being 60.10%.

Preparation Example 2 Preparation of a Polyacrylate Polyol

A reactor flushed with nitrogen and fitted with a condenser was chargedwith 759.61 parts by weight of solvent naphtha, and this initial chargewas heated to 145° C. with stirring.

In parallel to this, two separate feeds were prepared. Feed 1 consistedof 488.10 parts by weight of ethylhexyl methacrylate, 213.54 parts byweight of styrene, 183.04 parts by weight of n-butyl methacrylate,183.04 parts by weight of 2-hydroxyethyl acrylate, 457.60 parts byweight of 4-hydroxybutyl acrylate, and 32.50 parts by weight of acrylicacid. Feed 2 consisted of 62.54 parts by weight of solvent naphtha and152.53 parts by weight of peroxide TBPEH. When the temperature hadreached 145° C., feed 2 was metered in slowly and at a uniform rate overa time of 285 minutes. 15 minutes after the start of feed 2, feed 1 wasmetered into the reactor slowly and at a uniform rate over a period of240 minutes. After the end of the metered addition of feed 2, thereaction mixture was stirred for post polymerization at 145° C. for 120minutes more.

The solids content of the resulting product was determined as being65.65%, the acid number as 15.5 mg KOH/g (based on the solids), and theviscosity (at 23° C.) as 21 dPa s. The OH number was found to be 174.7.

Clearcoat Formulations

Experiment 3 - Experiment 1 - Experiment 2 - comparative referenceinventive example Acrylate resin from 59.04 59.04 59.04 preparationexample 2 Solvent naphtha 29.52 29.52 29.52 Triethyl 3.00 3.00 3.00orthoformate BYK 301 ® 0.32 0.32 0.32 surface additive TINUVIN 384-2 ®1.52 1.52 1.52 light stabilizer TINUVIN 292 ® 1.30 1.30 1.30 lightstabilizer NACURE 4167 ® 5.30 5.30 5.30 amine neutralized phosphatecatalyst Triethylamine 0 0 3.00 DBN 0 0.10 0 (30% strength solution inbutanol)

For the preparation of the 2K clearcoat materials, the followingmixtures were prepared from millbase and curing agent:

Experiment 3 - Experiment 1 - Experiment 2 - comparative referenceinventive example Addition of 100 100 100.1 103.0 parts by weight ofcuring agent as per preparation example 1 to the following amount ofmillbase

For the preparation of two-component (2K) clearcoats, the firstcomponents prepared in each case in accordance with the details abovewere homogenized with the below-mentioned amounts of the secondcomponent (curing agent as per preparation example 1) and applieddirectly after homogenization. For this purpose, metal test panels wereused which had each been coated with a customary and known cathodicallydeposited, thermally cured electrodeposition coat, a customary andknown, thermally cured surfacer coat, and a film, subjected topreliminary drying at 80° C. for 10 minutes, of a commerciallycustomary, conventional, black basecoat from BASF Coatings AG. Thebasecoat film and the clearcoat film were cured jointly at 140° C. for22 minutes. The resulting basecoat had a thickness of 7.5 μm, theresulting clearcoat a thickness of approximately 35 μm.

To evaluate the effect of the individual catalysts on the conversionrate in the isocyanate reaction, the conversion of the isocyanates wasmonitored by means of IR spectroscopy during the curing process at 140°C. over a period of 30 minutes. The corresponding results are compiledin Table 1.

Experiment 1 Experiment 2 Experiment 3 Isocyanate 40% 47% 17% conversionafter 5 minutes' curing at 140° C. Isocyanate 43% 53% 30% conversionafter 30 minutes' curing at 140° C.

Table 1: isocyanate conversion determined by IR spectroscopy for curingat 140° C. As the examples show, the isocyanate conversion is increasedby the addition of DBN, in comparison to the unmodified reference, by10% after 30 minutes. Even right at the beginning of curing, however, aconversion increased by 7% can be measured, in comparison to thereference specimen—experiment 1.

The results show that the formulation with DBN leads to an increasedisocyanate conversion, whereas the addition of triethylamine toformulations of this kind shows an opposite effect.

The evaluation of the further bands does not show any change duringcuring between experiment 1 and experiment 3, which suggests that thesilane crosslinking remains unaffected by the addition of DBN.

Concentrations of added amines higher than those shown in the examplesare preferably not to be used in the clearcoat formulations, since theylead to yellowing on overbake and also give rise to an unacceptable odornuisance.

It is general knowledge in the art that a higher isocyanate conversionleads ultimately to better product properties, in qualities includingweathering, by virtue of the fact that there is only very limitedoccurrence, or none at all, of aftercrosslinking reactions, which aremanifested more particularly in an improved acid resistance. Theinventive and comparative examples show that1,5-diazabicyclo[4.3.0]non-5-ene (DBN) and1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) have a positive influence onisocyanate crosslinking, while triethylamine (TEA) anddiazabicyclooctane (DABCO) have negative consequences.

The invention claimed is:
 1. A coating composition for application to asubstrate comprising (a) at least one hydroxyl-containing compound (A);(b) at least one compound (B) having free and/or blocked isocyanategroups; (c) at least one phosphorus-containing catalyst (C) comprisingphosphorus and nitrogen, for the crosslinking of silane groups; and (d)at least one further catalyst (D) that is a bicyclic amine, wherein oneor more constituents of the coating composition contain hydrolyzablesilane groups, the isocyanate groups react with the at least onehydroxyl-containing compound (A), and the resulting coating compositionis isocyanate-free; wherein, upon curing of the coating composition, acoat that is chemical- and weather-stable is formed.
 2. The coatingcomposition of claim 1, wherein the catalyst (D) is an unsaturatedbicyclic amine.
 3. The coating composition of claim 1, wherein thecatalyst (D) is 1,5-diazabicyclo[4.3.0]non-5-ene or1,8-diazabicyclo[5.4.0]undec-7-ene.
 4. The coating composition of claim1, wherein one or more constituents of the coating composition at leastpartly contain one or more, alike or different structural units of theformula (I)—X—Si—R″xG_(3-x)  (I) wherein G=identical or different hydrolyzablegroups, X=organic radical, R″=alkyl, cycloalkyl, aryl, or aralkyl, itbeing possible for the carbon chain to be interrupted by nonadjacentoxygen, sulfur or NRa groups, with Ra=alkyl, cycloalkyl, aryl oraralkyl, and x =0 to
 2. 5. The coating composition of claim 4, whereinone of more constituents of the coating composition contain between 2.5and 97.5 mol % based on the entirety of structural units (II) and (III),of at least one structural unit of the formula (II)—N(X—SiR″_(x)(OR′)_(3-x))_(n)(X′—SiR″_(y)(OR′)_(3-y))_(m)  (II) whereR′=hydrogen, alkyl or cycloalkyl, it being possible for the carbon chainto be interrupted by nonadjacent oxygen, sulfur or NRa groups, withRa=alkyl, cycloalkyl, aryl or aralkyl, X and X′=linear and/or branchedalkylene or cycloalkylene radical having 1 to 20 carbon atoms, R″=alkyl,cycloalkyl, aryl or aralkyl, it being possible for the carbon chain tobe interrupted by nonadjacent oxygen, sulfur or NRa groups, withRa=alkyl, cycloalkyl, aryl or aralkyl, n=0 to 2, m=0 to 2, m+n=2, and xand y=0 to 2, and between 2.5 and 97.5 mol %, based on the entirety ofstructural units (II) and (III), of at least one structural unit of theformula (III)—Z—(—X—SiR″_(x)(OR′)_(3-x))  (III), where Z=—NH—, —NR—, —O—, whereR=alkyl, cycloalkyl, aryl or aralkyl, it being possible for the carbonchain to be interrupted by nonadjacent oxygen, sulfur or NRa groups,with Ra=alkyl, cycloalkyl, aryl or aralkyl, x=0 to 2, and X, R′, and R″being as defined for formula (II).
 6. The coating composition of claim5, wherein one or more constituents of the coating composition containbetween 5 and 95 mol %, based in each case on the entirety of structuralunits (II) and (III), of at least one structural unit of the formula(II) and between 5 and 95 mol %, based in each case on the entirety ofstructural units (II) and (III), of at least one structural unit of theformula (III).
 7. The coating composition of claim 6, wherein thestructural elements (II) and (III) are present in fractions of 2.5 to97.5 mol %, based in each case on the sum of the functional groups forcrosslinking in the coating composition, formed from the fractions ofthe hydroxyl and isocyanate groups and from the fractions of thestructural elements (II) and (III).
 8. The coating composition of claim5, wherein the at least one compound (B) comprises at least one of thegroup of structural unit (I), structural unit (II), structural unit(III), and combinations thereof.
 9. The coating composition of claim 8,wherein, in the at least one compound (B), between 2.5 and 90 mol %, ofthe isocyanate groups in the polyisocyanate structure have undergonereaction to structural units (II) and between 2.5 and 90 mol % of theisocyanate groups in the polyisocyanate structure have undergonereaction to structural units (III), and the total fraction of theisocyanate groups in the polyisocyanate structure that have undergonereaction to structural units (II) and (III) is between 5 and 95 mol %.10. The coating composition of claim 8, wherein the polyisocyanatestructure is selected from the group of 1,6-hexamethylene diisocyanate,isophorone diisocyanate, and 4,4′-methylenedicyclohexyl diisocyanate,the biuret dimers of the aforementioned polyisocyanates and/or theisocyanurate trimers of the aforementioned polyisocyanates.
 11. Thecoating composition of claim 1, wherein the at least onehydroxyl-containing compound (A) comprises at least onepoly(meth)acrylate polyol.
 12. The coating composition of claim 1,wherein the catalyst (D) is present in the coating composition in anamount of 0.01% to 3% by weight, based on the solids content of saidcomposition.
 13. The coating composition of claim 1, wherein the atleast one phosphorus-containing catalyst (C) is selected from an amineadduct of an acyclic phosphonic diester, a cyclic phosphonic diester, anacyclic diphosphonic diester, a cyclic diphosphonic diester, an acyclicphosphoric diester or a cyclic phosphoric diester.
 14. A multistagecoating method which comprises applying a pigmented basecoat film to anuncoated or precoated substrate and thereafter applying a film of thecoating composition as claimed in any one of claims 1 to
 12. 15. Themultistage coating method of claim 14, wherein, following theapplication of the pigmented basecoat film, the applied basecoatmaterial is first dried at temperatures from room temperature to 80° C.and, following the application of the coating composition of claim 16,the system is cured at temperatures from 30 to 200° C. for a time of 1min up to 10 h.
 16. The multistage coating method of claim 15 whereinthe coating composition of claim 16 is a clearcoat material used inautomotive OEM finishing or automotive refinish.